Iron complexes of ethylene-bis-({60 -2-hydroxyaryl acetic acids

ABSTRACT

New iron complexes of ethylene-bis( Alpha -imino-2-hydroxyarylacetic acids) containing sulfonic acid groups are disclosed in which the molar ratio of iron to ligand is from about 1.1:1 to 3: 1. These complexes are stable at pH values of from about 6.0 to 9.0, and are useful for the treatment of iron deficiencies in plants.

United States Patent 1191 UNITED STATES PATENTS 2/1958 Dexter 260/439 R Petree et a1. Sept. 2, 1975 [54] IRON COMPLEXES OF 2,921,847 1/1960 Knell et a1 260/439 R ETHYLENE BIS 2 0 2,028,407 2/1962 Knell et a1... 260/439 R ACETIC'ACIDS 332233123 35133? 1512113313?" 1:: 5235233? [75] Inventors: Harris E, Petree, Spanish Fort; 3,711,525 1/1973 Hennart 260/439 R Joseph W. Stutts, Jackson, both of Primary ExaminerArthur P. Demers [73] Assignee: Ciba-Geigy Corporation, Ardsley,

22 Filed: Aug. 24, 1973 [57] ABSTRACT [21] A l N 391,401 New iron complexes of ethylene-bis(a-imino-2- hydroxyaryl-acetic acids) containing sulfonic acid groups are disclosed in which the molar ratio of iron 1 [52] US. Cl.2 260/439 R; 71/] to ligand is from about to These complexes [51] 'T C07F 15/02 are stable at pH values of from about 6.0 to 9.0, and FIGld Of Search R, J are useful for the treatment of iron deficiencies in lants. [56] References Cited p 6 Claims, No Drawings IRON COMPLEXES OF ETIIYLENE-BIS-( -2-HYDROXYARYL ACETIC ACIDS DETAILED DISCLOSURE The present invention relates to iron complexes of ethylene-bis-( a-imino-2-hydroxyary1 acetic .acids) containing one or more sulfonic acid groups at each of the aryl radicals in which the molar ratio of iron to ligand is from 1.1:] to 3:1. This invention further pertains to compositions containing said iron complexes as active substances and to methods of treatment of iron deficiencies in plants with said iron complexes.

It is known that iron ehelatcs of N,N-bis (o-hydroxybenzyl)-ethylenediaminediacetic acids and ethylenebis-( a-imino-Z-hydroxyphenylacetic acids), the phenyl radicals of which may be substituted by halogen atoms or alkyl, alkoxy, sulfonic acid or carboxylic acid groups, and derivatives thereof, are useful for the treat ment of iron deficiencies in plants and/or mammals. In these known chelates the organic molecule was combined with ferric or ferrous iron in a molar ratio of 1 1.

(See, e.g US. Pat. Nos. 2,921,847, 3,005,848, 3,038,793 and 3,367,834.)

The present invention provides new iron complexes which are more effective, and therefore more economical, in supplying micronutrients to plants. More particularly, complexesof a ligand and iron are provided, wherein the molar ratio of ligand to iron is from about 121.1 to 1:3, and wherein the ligand has the following formula coo M M ooc aromatic compounds of the formula:

OH OH OH monosulfonatcd Z-naphthol derivatives of the formula:

SOH

wherein SO,;l-l is in the 3,4,5,6,7 or 8 positions, and diand tri-sulfonie acid derivatives of Z-naphthol, with SO;,H groups being in the 3,4,5,6,7 or 8 positions.

Additionally, Ar represents oz-hydroxy-substituted anthracene or phenanthrene sulfonic acids of the formula qa x where X is l to 3.

Furthermore, available substituent points in the aromatic nucleus may be substituted, for enhancement of biological properties, by such groups as halogen atoms, lower alkyl, lower alkoxy, lower alkylthio ,l o'wer alkyl sulfoxy, lower alkylsulfone, nitro, aminoQlower alkylamino, lower dialkylamino and acylamid'o. Heterocyclic groups containing N, S, O, P, and other atoms are further possible substituents.

More particularly, complexes of ligands of an ethylene-bis-(a-imino-2-hydroxyary1acetic acid) having the general formula and iron are provided, wherein the molar ratio ofligand to iron is from 10:1,! to 1:0:3.0, and X, and X are each linked in the 3-, 4- or 5-position to each benzene nucleus and each represents SO -,M ,wherein M is hydrogen or an alkali metal ion.

If M represents an alkali metal ion, this may be lithium or potassium and, more especially, the sodium ion.

The substituents X, and X are each preferably linked in the 5-position to the respective benzene nucleus, and each represents SO;,M M being hydrogen or the sodium ion.

Iron complexes as defined are preferred wherein the molar ratio of ligand to iron is from about 1 1.5 or 1: 1.8 to l 2.0.

That ligands of formula I combine with iron .in a molar ratio of from about 1 1. l to 2.0 or 2 is surprising both in view of the teachings of the prior art and the finding that similar ligands, such as, N,N'-bis-(2- hydroxy-S-sulfobenzyl )-ethy1enediaminediacetic acids, are unable to chelate iron at molar ratios greater than one.

As regards the nature of the complexes of this invention, one iron is chelated by one of the ligands of formula I in the usual manner to form a 6-coordinate octahedral complex, but it is not known how additional second atoms of iron are bound to the ligand.

The ligands of Formula I are known per se (see c.g., U.S. Pat. No. 3,005,848) and can be prepared by conventional methods, as for instance by reacting a hydroxyphenylsulfonic acid, or an alkali metal salt thereof, with glyoxylic acid or an alkali metal salt thereof, especially sodium glyoxylate, and ethylenediamine, in a motor proportion of at least 2:2: 1. The reaction is advantageously conducted in an aqueous or aqueous-organic medium, at a temperature between about 70C and lO()C, preferably about 80 and 90C,.

and at a pH between 8 and 10. Suitable organic solvents are water-miscible solvents, such as methyl ethyl and isppropyl alcohol. It is also possible to use sodium dichloroacetate in place of the glyoxylic acid or its alkali metal salt, in the above synthesis. In this case, it is necessary, however, to add two moles of base for each mole of sodium dichloroacetate used in order to maintain the desired degree of alkalinity during the reaction.

Isolation of the ligand of Formula I from the resultant brown solution is not necessary, though possible, for instance by extraction of the dried reaction mixture with a suitable solvent such as methyl, ethyl or isopropyl alcohol, acetone, chlorinated hydrocarbons or dimethylformamide, at a pH value of the reaction mixture of about 1.0.

According to a preferred embodiment the solution of the desired ligand is treated directly, in a manner known per se, with a suitable water-soluble ferric salt, such as ferric chloride, sulfate, nitrate or acetate. Be-

fore the addition of the ferric salt, the pH of the reaction mixtureis advantageously adjusted to about 10.0 to l 1.0, e.g. by means of aqueous sodium hydroxide solution, and the solution is cooled to about to 50C. This temperature is maintained throughout the addition of the ferric salt, the latter being preferably employed in the form of an aqueous solution. The iron content of said aqueous solution of the ferric salt should be preferably somewhat in excess over the desired ligand/Fe molar ratio in the complex to be produced, e.g., an about 1030% excess over the ligand/Fe molar ratio of from about 1 1.1 to 1:3 should be employed. After all the ferric salt has been added, the pH value of the reaction mixture is again adjusted to about 6.5 to 8.0, preferably by the addition of aqueous sodium hydroxide solution. A red-purple solution is obtained. The complex can be isolated by known methods such as evaporating the reaction mixture to dryness.

Additionally, ferrous (Fe )salts may be used as sources of iron. In general, these will be transformed to ferric or ferroso-ferric complexes due to the tendency of these to approach the Fe oxidation state by abstraction of oxygen from air, ligand, or reaction mixture.

It is also possible to use sodium dichloroacetate in place of the glyoxylic acid or its alkali metal salt, in the above synthesis. In this case, it is necessary, however, to add two moles of base for each mole of sodium dichloroacetate used in order to maintain the desired degree of alkalinity during the reaction.

In contrast to prior art compositions the complexes of this invention meet also present day ecological needs: These complexes may be prepared in simple chemical reactors (stirred vessel equipped for heating or cooling). The chelation may be accomplished in the same vessel, and, since the entire mixture is a soluble. stable solution, it can be isolated by drying (or used as is). In either case no effluent is generated by this process, and no biological, chemical or total oxygen demand byproducts are present which require effluent treatment. Furthermore, due to the higher iron to ligand ratio the amount of iron complex for treatment of iron deficiencies may be reduced. The product, when dried, is a crystalline solid which is dense (55 lbs/cu. ft), rapidly and readily redissolves in water for its application as an agricultural nutrient, and is free flowing and relatively non-dusting, an advantage over earlier discovered materials such as CHEL 138 NaFe (EDDHA NaFe, or, ethylenediaminedi-2-hydroxyphenyl-acetic acid, NaFe salt).

The following examples serve to illustrate the preparation of the novel iron complexes of the present invention but are not to be considered limiting.

EXAMPLE I Ferric Complex of Ethylene-bis-( oz-imino-2-hydroxy-5-sulfophenylacetic Acid).

To a reaction flask were added 100 g of water, 528 g. (2.0 mol) of a 66% aqueous solution of pphenolsulfonic acid, and 296 g. (2.0 mol) of 50% glyoxylic acid. Then 335 g. (4.2 mol) of a 50% aqueous sodium hydroxide solution were slowly added at 30C until a pH of 6.0 was reached. Finally, 66 g. 1.0 mol) of 92% ethylenediamine were charged at the same temperature, and the pH of the reaction mixture was adjusted to 9.0 by the addition of further aqueous sodium hydroxide solution. The reaction mixture was heated to C for 4 hours. After completion of the reaction mixture was cooled to 40C, and the pH thereof was raised to 10.8 to l 1.0 by the addition of 50% aqueous sodium hydroxide solution. An assay of the solution by copper chelometric titration analysis showed a yield of product ethylene-bis-( oz-imino-Z-hydroxy-S-sulfophenylacetic acid) of 70.0%. 784 g. ferric sulfate solution as 10% Fe 1 .4 g.-atoms) were then slowly added at 40-50C, followed by the addition of 50% aqueous sodium hydroxide solution to adjust the pH to 6.5. The solution became deep red, and was then evaporated to dryness. The yield of the solid was 1045 g; Fe 7.5; molar ratio ligand: Fe 1:2.

EXAMPLE 2 Ferric Complex of l ,1 '-ethylene-bis-( aimino-2-hydroxy-3 ,6-disulfo-2- naphthaleneacetic) Acid Similarly to the above, to a 3 1. reaction flask were charged 1300 g. of water, 696 g. (0.81 mol) of Z-naphthol3,6-disulfonic acid, Na salt, (R Salt) and 296 g. (2 mol) of 50% glyoxylic acid. The mixture was cooled to ()10C and 66 g. (l g-mol) of 91.5% ethylenediamine in water was added, allowing the mixture to reach 25C and a pH of 3.5. The mixture was then heated at 45C for four hours; a final pH of 3.1 was noted. Copper chelometric titration analysis indicated an 82% yield of 1,1-ethylene-bis-(a-imino-2-hydroxynaphthalene-3,6-disulfo-acetic) acid. Chelation with iron was carried out in two steps. First, a 1:1 Fe:ligand chelate was synthesized by charging 291.4 g FeCl solution (4571) based on copper chelometric assay of the ligand solution. Adjustment to pH 7 was carried out by addition of 456 g of 25% NaOH. Assay of the chelate solution spectrophotometrically showed a 1.37% soluble Fe content and the insolubles were measured at only 0.01%. After allowing for analytical sample removal, a second mole-equivalent of Fe was added by charging 266.4 g. FeCL, solution. After pH adjustment to 7 again the product solution was dried on a pilot plant drum dryer resulting in chelate containing 7.0% soluble Fe.

The iron complexes of the present invention are stable over a wide pH range, i.e., pH values ranging from about 6.0 to 9.0 and are thus suitable for the treatment of iron deficiencies occurring in plants grown on a1kaline as well as neutral and slightly acid soils. The present invention thus also provides a composition for the treatment of iron deficiencies in plants which comprises, preferably. from about one-hundredth to about fifty percent by weight, of at least one complex of a ligand of Formula I and iron as hereinbefore defined, as active ingredient. Said compositions are applied in effective amounts as any other plant food. The active ingredient may be admixed with other solids and applied as a conventional solid fertilizer, or it may be put into 6 corporated into the surface at the rate of 2 ppm Fe. Leaf yields (mg/plant) and soil Fe (ppm) was measured after the soybeans were grown to indicate the effect of the treatments.

Leaf Yield ppm Fe mg/plant of soil Check 170 29 (GA-20724 at 2 ppm Fe 54] 51 The check plants were small and showed iron chlorosis of the leaves while the treated plants were green and healthy.

Leaf Dry weight Fe content Leaf mg/plant of leaves( ppm) Color Cheek 220 20 Yellow (G/M20724 at 1.5 lbs. Fc/A 503 30 Green vwell as the results obtained by such treatment.

EXAMPLE 3 GIANT BETSY ROSS CHRYSANTHEMUM in a greenhouse test Chrysanthemums were grown in a quartz sand culture. A high pH nutrient solution was added to the growing medium. In the check treatment iron was withheld while in the other treatment the Example 1 iron complex (hereinafter CGA 20724) was added to the nutrient solution to supply iron. Visual observations of the growing plants were taken 9 and 17 days following treatment to measure the effect of the iron treatment.

Check plots had poor growth and remained yellow showing severe iron chlorosis while treated plants grew vigorously and remained green and healthy.

EXAMPLE 6 HARDEE SOYBEANS Soybeans were grown in onegallon plastic tubs in a soil which had a pH of 8.0. CGA-20724 was added to the pots and lightly incorporated into the soil surface. Four replications were used in the test. After the plants were grown they were harvested and green weight yields taken to indicate treatment effect. Also leaf Fe content was determined by plant analysis to show iron uptake.

Green Weight (gms) Leaf lron of Soybean Plants ppm Fe Chlorosis Ratings Check 63.9 69 9 days 17 days CGA-20724 at 0.6 lbs. Fe/A 81 80 Check Very Severely chlorotic chlorotic GOA-2072 1 s Fv/wbw Plants treated with CGA-20724 produced higher yields foot of growmg medium Green Very green EXAMPLE 4 Soybeans were grown under controlled greenhouse conditions in pots in a high pH soil. The soil pH was 8.5. CGA2()724 was added to the soil and lightly inand had higher leaf Fe content than untreated plants.

EXAMPLE 7 BRAGG SOYBEANS CGA-20724 was applied in a single band injected into the soil to the side and below the soybean seeds. The soil in which the test was run had a high pH.

The soybeans were grown for 60 days and then fivefoot plots were harvested and weighed. Green weights indicated response to treatments. Three replications were included in the test.

Green Weight of Soybean Plants Check CGA-20724 at 0.15 lbs. Fe/A 33.7 ounces 46.0 ounces The CGA-20724 treatment increased the size and weight of the soybean plants.

EXAMPLE 8 ANOKA VARIETY SOYBEANS 8 showed poor growth and were yellow while the treated plants were growing well. were green and healthy.

EXAMPLE l NAVEL ORANGES Days After Treatment Application 0 30 I 240 18.75 gms Fe/tree Cheek Slightly chlorotic Slightly chlorotic Green Green Green Slightly chlorotie Moderately Very chlorotie chlorotic In a pot test with 5 gal. plastic tubs containing high pH iron deficient soil, 4 replications, grown outdoors, CGA-20724 iron chelate was added to the soil and mixed in the surface layer. Beans were planted, evaluated for greening response and shoot weights were taken at harvest.

Foliar Greening Response Early rating Late rating CGA-20724 at 0.9 lbs. Fe/A Cheek The higher number over the check shows greening due to supply of Fe from CGA-20724. Therefore at both ratings, early and later in the growth cycle, the treated plants were much healthier than the checks.

Shoot Weights at Harvest CGA-20724 at 0.9 lbs. Fe/A Check Plants treated with CGA-20724 had higher shoot weights than untreated plants.

EXAMPLE 9 SOYBEANS In a greenhouse pot test with 4 replicates CGA- 20724 iron chelate was added to a high pH iron deficient soil and mixed into the surface layer of the soil. Beans were planted. Greening responses, iron content of the leaves, and shoot weights were taken to determine response from the treatments.

Application Fe ppm of Shoot yield rate dry weight mg dry wt/ lhs.Fe/Acre (leaves) plant Greening ()(check) 33 '16] Yellow 0.5 42 410 Green and healthy Iron content of the leaves and shoot weights were statistically higher than the check. The check plants Response of the trees as measured by greening effect on the leaves was excellent from the treatments. Untreated trees showed iron chlorosis on the leaves and die-back of terminal growth because of iron deficiency. Cheek trees produced a very poor crop of oranges while treated trees produced good fruit.

EXAMPLE ll VANGUARD LETTUCE CGA-20724 was applied to the soil in two bands on either side of the lettuce crop. Four replications were used in the test. Response of the treatments was measured by leaf analysis of the plants for iron to show if the iron was supplied to the crop by CGA-20724.

Leaf analysis ppm of Fe Whole Plant Petioles Petioles early early late Check 23l 3 l() 84 CGA-20724 at 0.9 lbs. 251 460 I02 FE/A CGA-20724 as a soil application to lettuce did supply iron to the growing crop as shown by the leaf analysis data.

EXAMPLE l2 MCCASLAN 42 POLE BEANS CGA-20724 was applied as a soil drench treatment two weeks after seeding pole beans. Four replications were used in the test which was on a high pH iron deficient soil. The beans were grown to maturity and harvested. Yields were used to indicate treatment response.

Market Yield Dollar Value/A Cwt/A at $6.0(l/bushel Check 45 S900 CGA-20724 at 0.6 lbs. Fe/A 49 $960 The CGA-20724 increased the yield of pole beans.

EXAMPLE l3 PEANUTS In a field test on peanuts growing on soil low in available iron with four replications. (GA-20724 was applied as sidedressing to the soil soon after the peanut crop emerged. Treatment response was measured by yield data.

lbs/A Fe Yield of Peanuts Applied ()(eheck) 920 0.3 lbs. Fe/A 1072 The yield of the treated peanuts were statistically,

higher than the check. Iron ehlorosis of the leaves was evident during the growing season in the untreated plots.

EXAMPLE l4 BARTLETT PEAR VARIETY Foliar Greening Response Check 25 (GA-20725 at 25 gms Fe/tree 4.5

Rating scale I Severe chlorosis 2 Very Chlorotic 3 Slightly chlorotic 4 Pale green 5 Dark green Treated trees were very green and healthy compared to the check. No signs of iron deficiency of the leaves were noted on the treated trees.

What is claimed is:

1. Iron complexes of ethylene-bis-(aimino-2- hydroxyaryl acetic acids) of the furmula wherein Ar is selected from the group consisting of OH on OH I i i so a Ho S 3 so H 3 3 l 0H OH so H a) x (so n) l -OH on (SO3H)X wherein X is l to 3 the molor ratio of ligand to iron being from about 1 1.] to l :3.().

2. Iron complexes as claimed in claim 1 wherein the molar ratio of ligand to iron is from about 1 1.8 to l 2.0.

3. Iron complexes as claimed in claim 1 wherein the ethylene-bis-( a-imino-2-hydroxyaryl acetic acids) have the formula OH OH C OOH HOOC wherein X and X are each linked in the 3-, 4- or 5- position to the respective benzene nuclei and each represents -SO;,H and wherein the molar ratio of ligand to iron is from about 121.8 to 112.0.

4. Iron complexes as claimed in claim 3 wherein X and X. are each linked to the respective benzene nuclei in the 5-position.

5. Iron complexes as claimed in claim 3, wherein the ethylene-bis-(a-imino-Z-hydroxyaryl acetic) acid is ethylene-bis-( oz-imino-Z-hydroxy-S-sulfophenyl acetic) acid.

6. Iron complexes as claimed in claim 1, wherein the cthylene-bis(a-imino2-hydroxyaryl acetic) acid is 1.1 -ethylene-bisa-imino-2-hydroxy-3 ,6-disulfo-2- naphthalene acetic) acid. 

1. IRON COMPLEXES OF ETHYLENE-BIS-(A-IMINO-2-HYDROXYARL ACETIC ACIDS) OF THE FORMULA
 2. Iron complexes as claimed in claim 1 wherein the molar ratio of ligand to iron is from about 1 : 1.8 to 1 : 2.0.
 3. Iron complexes as claimed in claim 1 wherein the ethylene-bis-( Alpha -imino-2-hydroxyaryl acetic acids) have the formula
 4. Iron complexes as claimed in claim 3 wherein X1 and X2 are each linked to the respective benzene nuclei in the 5-position.
 5. Iron complexes as claimed in claim 3, wherein the ethylene-bis-( Alpha -imino-2-hydroxyaryl acetic) acid is ethylene-bis-( Alpha -imino-2-hydroxy-5-sulfophenyl acetic) acid.
 6. Iron complexes as claimed in claim 1, wherein the ethylene-bis-( Alpha -imino-2-hydroxyaryl acetic) acid is 1,1''-ethylene-bis-( Alpha -imino-2-hydroxy-3,6-disulfo-2-naphthalene acetic) acid. 